Heating system

ABSTRACT

One embodiment of the invention, is a heating system, including a heat source for heating a medium, a circulation system for circulating heated medium; a control system for controlling the temperature to which the medium is heated in accordance with a temperature set point. An energy monitor generates a measure of energy consumed by the system, which is arranged for a predetermined period to set a fixed temperature set point. For a subsequent period the temperature set point is set dependent on the energy used in the predetermined period.

This invention relates to heating systems.

One of the problems in managing a heating system for moderate and large buildings is that there is no single position in the build in which the temperature is sufficiently representative to use as feedback for controlling the boiler. Attempts have been made to control the system in accordance with demand by measuring the temperature of the return to the boiler. Improvements are still desired.

Against this background, in accordance with one aspect of the invention, there is provided a heating system, including a heat source for heating a medium, a circulation system for circulating heated medium; a control system for controlling the temperature to which the medium is heated in accordance with a temperature set point; and an energy monitor for generating a measure of energy consumed by the system, wherein the control system is arranged for a predetermined period to set a fixed temperature set point, and to set the temperature set point for a subsequent period dependent on the energy used in the predetermined period. The energy used by the system depends on the efficiency, e.g. of the boiler, on the heat loss and on demand. Efficiency and heat loss are temperature dependent, thus by fixing the temperature to which the medium, e.g. water, is heated, changes in the energy from one predetermined period to another represent the demand, higher on cold days, lower on hot days. A measure of demand is thus obtained which is used to control the temperature of the water supplied by the boiler. The system can be used without reference to outside temperature.

A preferred system utilises a burner for providing heat to the heat source to heat the medium, and the energy monitor is arranged to measure the accumulated on time of the burner in the predetermined period.

In such a system in which the burner is operable at different fuel consumption levels, the energy monitor is arranged to measure the accumulated on time of the burner at each consumption level.

In a preferred form, the heat source is a boiler, the medium being water.

Preferably, the temperature set point for water supplied by the boiler, for the subsequent period is proportional to the measure of energy consumed in the predetermined period.

Another aspect of the invention is based on the observation that in a heating system where individual radiators are fitted with thermostatic valves, the demand, as measured by rate of fuel use, for example, fluctuates in response to local space controlled temperature and reduces from a high start during daylight hours. In a system where individual radiators are not fitted with thermostatic valves, the demand is much less variable resulting either in the occupants of the building being uncomfortably cold e.g. in the morning or uncomfortably warm e.g. later in the day or, possibly both.

Against this background, in accordance with a second aspect of the invention, there is provided a heating system, including a heat source for heating a medium, a circulation system for circulating heated medium; a control system for controlling the temperature to which the medium is heated in accordance with a set point and arranged to derive the set point dependent on two independent functions one of which reduces in accordance with a predetermined regime, during the passage of daylight hours. A heating system which has no (or few) thermostatic radiator valves, can thus be forced to use energy in the same pattern as one which has thermostatic radiator valves, which saves energy and money, and provides a more comfortable environment for the occupants.

In an alternative aspect, the invention provides a heating system, including a heat source for heating a medium, a circulation system for circulating heated medium; a control system for controlling the temperature to which the medium is heated in accordance with a temperature set point; and an energy monitor to generate a measure of the energy consumed by the system in successive periods during daylight hours; the control system being arranged to determine on an initial day whether or not the energy consumed in successive periods reduces significantly, and if it does not, on subsequent days to reduce the temperature set point during the passage of daylight hours. The system thus automatically sets itself in accordance with the presence or absence of thermostatic radiator valves.

A preferred embodiment includes a burner for providing heat to the heat source to heat the medium, and the energy monitor is arranged to measure the accumulated on time of the burner in each the successive period. Although there may be inaccuracies due to differing fuel pressures and differing calorific values, for example, the on time measurement is sufficiently accurate for the purpose.

If in that arrangement, the burner is operable at different fuel consumption levels, the energy monitor is arranged to measure the accumulated on time of the burner at each consumption level.

In a preferred example, the heat source comprises a boiler, the medium being water.

The other function may be of measured or inferred parameters, e.g. outside temperature.

Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings in which:

FIG. 1 is a block diagram of a heating system embodying the invention;

FIG. 2 is a graph useful in explaining the operation of the system of FIG. 1 embodying the first aspect of the invention; and

FIG. 3 is a graph useful in explaining the operation of FIG. 1 embodying the second aspect of the invention.

Referring to the drawings, a building 2 is heated by circulating a medium, e.g. air or water, heated by a heat source. In one example the water is circulated by a pump through radiators, not shown, from a boiler 4. A temperature sensor 6 senses the temperature of the hot water outlet 8 of the boiler 4. A temperature controller 10 responds to the sensor 8 to switch the boiler on or off to maintain the temperature of the outlet water within limits from a nominal temperature set point input from a set point controller 12. Alternatively, the upper and lower limits either side of the nominal temperature set point may be input from the controller 12. In either event, the temperature controller switches the boiler on at the lower limit point and off at the upper limit.

In embodying the first aspect of the invention, so that the boiler operates in accordance with demand for heat, the system is run for an initial predetermined period each day with the nominal temperature set point fixed at the same temperature every day, e.g. 70° C. The initial period may, for example, be an hour before the building is occupied and the first hour after that. During this period, the set point controller logs the time the boiler is switched on to accumulate a total burn time in the period. This is fairly closely representative of the total fuel and thus energy used in this period. Inaccuracies may arise from variations in such things as calorific value of the fuel and the pressure with which it is delivered, but in practice the measurement is accurate enough to provide an improvement in control of the system.

The measured demand is then used to derive a water set point temperature using the relationship shown in FIG. 2 which is linear between 90% demand and 10% demand. Thus on a warm day, the energy demand to maintain a water temperature of 70° C. is low and the water set point used for the subsequent period is low. On a colder day, the energy demand required to maintain the water temperature at 70° C. in the initial period is higher and the temperature set point used for the subsequent period is higher.

If the boiler is operable at more than one fuel consumption level, e.g. so called high burn and low burn, the times for which the boiler operates at each level is logged separately and a figure for the total demand in the period is derived.

In embodying the second aspect of the invention, either additionally or alternatively, when the heating system is commissioned, it is run for a day and during daylight hours the a measure of the energy input or demand is monitored. To this end the set point controller uses an algorithm which may be conventional or may embody the first aspect of the invention, for determining the temperature set point as a function of measured or inferred parameters and logs the time the boiler is switched on to accumulate a total on time during each of successive periods, e.g. of one hour each. The conventional algorithm may take into account outside temperature, for example. The boiler on time for each hour is a measure of the total energy input or demand during the hour. In FIG. 3 the curve 14 is representative of the kind of energy input which would be detected if the radiators had thermostatic valves and falls off during daylight hours even if the temperature set point is fixed. Curve 16 is representative of the kind of energy input which would be detected if the radiators were not fitted with thermostatic valves and the temperature set point is fixed. The energy input is more or less constant throughout the day leading to less comfortable conditions in the building at one or both ends of the day.

During its commissioning run, the set point controller 12 examines the energy usage as represented by the boiler on time and, if it detects a relatively falling usage 14 continues to determine the set point only as a function of the measured or inferred parameters for each subsequent day. If a relatively constant usage 16 is detected, on subsequent days, the temperatures set point is determined by multiplying the function of measured or inferred parameters by a falling function such as that illustrated at 18 so as to force the usage to correspond to what would be obtained by use of thermostatic radiator valves.

It may be noted that this forcing function can be applied to warm air heating systems as well as radiator systems. 

1. A heating system, including a heat source for heating a medium, a circulation system for circulating heated medium, a control system for controlling the temperature to which the medium is heated in accordance with a temperature set point; and an energy monitor for generating a measure of energy consumed by the system, wherein the control system is arranged for a predetermined period to set a fixed temperature set point, and to set the temperature set point for a subsequent period dependent on the energy used in the predetermined period.
 2. A heating system as claimed in claim 1, including a burner for providing heat to the heat source to heat the medium, and wherein the energy monitor is arranged to measure the accumulated on time of the burner in the predetermined period.
 3. A heating system as claimed in claim 2, wherein the burner is operable at different fuel consumption levels, and wherein the energy monitor is arranged to measure the accumulated on time of the burner at each consumption level.
 4. A heating system as claimed in claim 2, wherein the heat source comprises a boiler, the medium being water.
 5. A heating system as claimed in claim 1, wherein the temperature set point for water supplied by the boiler for the subsequent period is proportional to the measure of energy consumed in the predetermined period.
 6. A heating system, including a heat source for heating a medium, a circulation system for circulating heated medium; a control system for controlling the temperature to which the medium is heated in accordance with a set point and arranged to derive the set point dependent on two independent functions one of which reduces in accordance with a predetermined régime, during the passage of daylight hours.
 7. A heating system, including a heat source for heating a medium, a circulation system for circulating heated medium; a control system for controlling the temperature to which the medium is heated in accordance with a temperature set point; and an energy monitor to generate a measure of the energy consumed by the system in successive periods during daylight hours; the control system being arranged to determine on an initial day whether or not the energy consumed in successive periods reduces significantly, and if it does not, on subsequent days to derive the set point dependent on two independent functions one of which reduces in accordance with a predetermined régime during the passage of daylight hours.
 8. A heating system as claimed in claim 6, including a burner for providing heat to the heat source to heat the medium, and wherein the energy monitor is arranged to measure the accumulated on time of the burner in the each successive time period.
 9. A heating system as claimed in claim 8, wherein the burner is operable at different fuel consumption levels, and wherein the energy monitor is arranged to measure the accumulated on time of the burner at each consumption level.
 10. A heating system as claimed in claim 6, in which the heat source comprises a boiler, the medium being water.
 11. A heating system as claimed in claim 6, wherein the other function is of measured or inferred parameters. 